Degradable composite material, its disposable products and processing method thereof

ABSTRACT

There is disclosed a kind degradable material and its disposable products, and their manufacturing process. The primary raw material used in the process consists of powdered shell or stalk of crops, urea-formaldehyde resin, and melamine resin. The materials are mixed thoroughly and hot pressed in a single step forming of the products. Oven drying or spray coating is not needed in the process. The products have the following characteristics: simple formula, simple process, low price; and the following properties: with natural color, dense; tough and tensile; and easy for coloring. In addition, they are water, heat and freezing resistant, anti-corrosion, non-poisonous, anti-pollution and biodegradable. They are entirely new environmental protection green products.

TECHNICAL FIELD

[0001] This invention relates to a kind of degradable material, itsdisposable products and processing method thereof.

BACKGROUND OF THE INVENTION

[0002] Currently, disposable tableware products made of plastic foam andplastics have the following defects:

[0003] (1) Large consumption of petroleum resources;

[0004] (2) Freon used in the foaming process destroys the ozone layer ofatmosphere;

[0005] (3) Inability to decay even if buried underground for 200 years,causing serious white pollution, etc.

[0006] At present, disposable tableware products substituted by paper orstarch materials have the following shortcomings: paper materialsconsume a large amount of bamboo and wood, thus damaging green resourcesin addition to causing water pollution by the pulp and paper productionprocess, while substitutes by starch material consume huge quantity ofgrains, and are susceptible to mildew. Apparently, such substitutesstill have technical problems as well as environmental problems thatneed to be addressed.

[0007] Most of the published patents for utilization of shell or stalkof crops as raw materials to make disposable tableware products use wetand cold pressing processes, requiring low temperature heating, longtime drying and repeated coating, and, thus, resulting in multiple stepsin operation, complicated processes, large amount of investment, highcost of the products, and difficulties in their promotion andpopularization. A small portion of the said published patents use dryand hot pressing process, but the organic high molecular polymer used asadhesives is expensive, and some of the adhesives do not meet sanitarystandards. Although the processes are simple, but the costs of theproducts cannot be reduced to a level acceptable in the markets.

SUMMARY OF THE INVENTION

[0008] In view of the defects and shortcomings of the above-statedprocesses for producing disposable tableware products by using shell orstalks of crops as raw materials, one object of the present invention isto provide a degradable composite material.

[0009] Another object of the present invention is to provide anapplication of the degradable composite material in manufacturing ofdisposable tableware.

[0010] The further object of the present invention is to provide amolding process method using the degradable composite material in themanufacturing of disposable tableware.

[0011] The degradable composite material of the invention comprises thefollowing components by weight and in parts: plant fiber: 60-90 partsurea-formaldehyde resin 10-35 parts melamine resin  3-10 parts foodcoloring agent  1-10 parts

[0012] wherein the molecular weight of the urea-formaldehyde resin is300-600.

[0013] The plant fiber used in this invention is crop hull or stalk andits amount is preferably in the range of 70 to 80 parts by weight.

[0014] In this invention, the molecular weight of the urea formaldehyderesin is 300-600, preferably 300-400. The urea-formaldehyde resin doesnot contain fluorescent brightening agent or sizing. Theurea-formaldehyde resin can be prepared by the following method:

[0015] 1. Formulation (by Weight and in Parts): urea 80-100 partsformaldehyde (37%) 160-240 parts sodium 5-10 partsdibutylnaphthalenesulfonate Resorcin 2.5-7.5 parts Glycerol 16-24 partspH value conditioner appropriate amount

[0016] 2. Preparation Method:

[0017] (1) According to the weight parts mentioned above, add urea,formaldehyde (37%) and glycerol into a reaction vessel with an agitatorand stir them at a 60° C. until the urea is fully dissolved to form afirst mixed solution. Cool the first mixed solution to 20-25° C. and addsodium diphenylnaphthalenesulfonate and Resorcin according to the saidweight parts. Then stir above mixture for about 10-60 minutes at arotation speed of 120 rpm to form a second mixed solution.

[0018] (2) Adjust the pH value of the second mixed solution to 7-8 witha pH value conditioner, then stir it for 30 minutes at a rotate speed of180-260 rpm, and stir it for another 30 minutes at a rotate speed of300-400 rpm to form a third mixed solution. Then pour the third mixedsolution into a storage and dry it in the dark for 24 hours to obtain anurea formaldehyde resin base material. Warm and dry theurea-formaldehyde resin base material for 6 hours at 60° C., and thenretain the final urea formaldehyde resin for later use.

[0019] The pH value conditioner utilized is either oxalic acid, aceticacid or phosphoric acid, preferably oxalic acid.

[0020] The amount of the melamine is preferably in the range of 3 to 5parts by weight.

[0021] The food coloring agent of the invention is selected from thegroup consisting of titanium white, zinc oxide, iron oxide red, pigmentyellow 147, pigment blue 15, and combinations thereof. Preferably, it istitanium white. The amount of the food coloring agent is in the range of3 to 5 parts by weight.

[0022] The processing method for manufacturing tableware product usingthe degradable composite material of the invention comprises thefollowing steps:

[0023] (1) pulverize the plant shell or stalk of crops into 60 mesh orover, and then mix the pulverized shell or stalk of crops withurea-formaldehyde resin and melamine resin proportionately andthoroughly to form a mixture of the biodegradable composite material;

[0024] (2) feed the mixture of the biodegradable composite material intothe concave molding mould positioned in a pushing upward type oilhydraulic press in a fixed quantity and position with temperature of themould maintained at 125-190° C.;

[0025] (3) control the pressure of the oil hydraulic press at between10-30 Mpa and keep the press operating at 3 intervals by maintaining atabove pressure for 3-30 seconds per each interval, so as to obtain thefinished products.

[0026] Preferably, the grinder is a turbine grinder, and maintain theconcave mould temperature at 160° C., the convex mould temperature at170° C., working pressure at 25 Mpa, keep the press operating at 3intervals by maintaining at above pressure for 3 seconds per eachinterval.

[0027] The invention will be better understood on reading the followingdetailed description of non-limiting embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE 1 The Preparation ofUrea-Formaldehyde Resin

[0028] (1) Formulation urea 20.9 kilogram formaldehyde (37%) 41.8 litersodium dibutylnaphthalenesulfonate 1.57 liter resorcin 1.05 kilogramglycerol 4.18 liter oxalic acid appropriate amount

[0029] (2) Preparation Method:

[0030] 1. Add urea, formaldehyde (37%) and glycerol into a reactionvessel with an agitator and stir them at a 60° C. until the urea isfully solved to form a first mixed solution. Cool the first mixedsolution to 20-25° C. and add sodium diphenylnaphthalenesulfonate andresorcin according to the said weight parts. Then stir above mixture forabout 10-60 minutes at a rotate speed of 120 rpm to form a second mixedsolution.

[0031] (2). Adjust the pH value of the second mixed solution to 7-8 withoxalic acid, then stir it for 30 minutes at a rotate speed of 180-260rpm, and stir it for another 30 minutes at a rotate speed of 300-400 rpmto form a third mixed solution. Then pour the third mixed solution intoa storage container and dry it in the dark for 24 hours to obtain anurea-formaldehyde resin base material. Warm and dry theurea-formaldehyde resin base material for 6 hours at 60° C., and then toobtain the final urea-formaldehyde resin for later use.

EXAMPLE 2 Manufacture the Degradable Disposable Tableware

[0032] Crush the dried crop hull to fines up to 60 mesh by a turbinegrinder produced by Hangzhou Chemical Industry Institute for spare.

[0033] According to the Formulations listed in table 1, add fine cropbull, urea-formaldehyde resin dry ester (prepared in example 1),melamine resin (produced by Nanjing ally resin factory), and whitetitanium pigment into an upright blender and stir it for about 15minutes until it is homogeneous. 5 kinds of degradable compositematerial can be achieved. TABLE 1 Formula Formula Formula 3 Formula 4Formula 5 Component 1 (kg) 2 (kg) (kg) (kg) (kg) Crop hull 19.25 15 17.540 22.5 Urea- 3.75 6.75 8.75 2.5 Formaldehyde Resin Melamine Resin 1.250.75 2.25 2.5 White Titanium 0.75 2.5 6.25 0.25

EXAMPLE 3 Manufacture the Degradable Disposable Tableware

[0034] According to the process condition indicated in table 2, make thedisposable tableware by the degradable composite material achieved fromexample 1. Each disposable tableware will use 30 grams of the degradablecomposite material in the concave mold of the oil hydraulic press.

[0035] Compare the capability, appearance and cost of the products, theproduct made by the degradable composite material from formula 1 ispreferable. TABLE 2 Process Formula Formula Parameter 1 2 Formula 3Formula 4 Formula 5 Concave 160 150 140 130 115 Temperature/° C. Convex170 160 150 140 125 Temperature/° C. Pressure/M Pa 25 23 21 19 17Pressure Keeping 3 10 17 24 30 Period/s Pressure Keeping 6 5 4 3 2Times/times Deflation Time/s 3 5 7 9 12 Deflation 8 8 8 8 8 Gap/mm

EXAMPLE 4 Test of Evaporated Residues and Fluorescent Material of theProduct

[0036] The sample tested was the disposable tableware product producedin example 1 herein using specifically Formula 1 disclosed therein.Standard testing standard GB 5009.60-85 was used. The results are shownin Table 3 below. TABLE 3 Normalized Test items Measured value valuen-hexane evaporated residue mg/L 4.8 ≦30  4% acetic acid evaporatedresidue mg/L 11.2 ≦30 65% alcohol evaporated residue mg/L 3.8 ≦30Fluorescent test (254 nm and 365 nm) Qualified ≦5 cm²/100 cm²

[0037] As shown in Table 3, it was indicated that the result ofevaporated residues and fluorescent test could reach the requirements ofrelated test standards.

EXAMPLE 5 Biodegradability Experiments of the Product

[0038] 1. Sample: The disposable tableware produced by formula 1 ofexample 1

[0039] 2. Biodegradability Experiments (designed referring to U.S. ASTMmethods)

[0040] (1). Bacterial Strains:

[0041]Aspergillus niger B1

[0042]Trichoderma reesai 9414

[0043] Trichoderma sp. 108

[0044] Gibberella sp. ST-3

[0045] Pseudomonas sp. 29

[0046]Bacillus cereus 45

[0047] Bacillus sp. W31

[0048] (2). Culture Medium: A. Czapek medium: NH₄NO₃    2 g, K₂HPO₄    1g, MgSO₄.7H₂O  0.5 g, KCl  0.5 g, FeSO₄.7H₂O  0.01 g, Agar   15 g, Fineexperiment material   30 g, H₂O  1000 ml pH 6 (used for fungi) pH 7(used for bacteria) B. Broth Bouillon Medium: Bouillon Ointment    3 g,Peptone   10 g, NaCl    5 g, Agar   15 g, H₂O  1000 ml, pH 7.0-7.2.

[0049] 3. Method and Result

[0050] Measure the growth of fungi by means of a dibbling method: Takethe Czapek agar medium which has been mixed with fine experimentalmaterial as the carbon source and pour into a 9 cm-diameter glassculture plate after having been melted, then mix it lightly to behomogeneous and cool to coagulate. Inoculate some mycelial or spores ofthe fungi with an inoculating needle in the central part of the cultureplate or in a triangle figure. Grow them at a temperature of 28° C. for10 days and 20 days respectively, and then measure the diameter of everycolony as to show its growth. From the result shown below in table 4,all of the four strains of fungi can grow on the Czapek agar mediummixed with experimental material. Although their growth is slow, itstill can prove that these fungi can utilize the experiment material ascarbon and energy sources to grow. TABLE 4 Scope of Colony (diameter mm)Fungi 10 days 20 days Aspergillus niger B1 3-4 4-5 Trichoderma reesai9414 2 3 Trichoderma sp. 108 0.8 1 Gibberella sp. ST 0.8 1

[0051] Measure the growth of bacteria by means of a shaking bottlemethod: Take some bacteria from the fresh bouillon agar slope with aninoculating ring and inoculate them onto 50 ml Czapek agar medium whichuse experimental material as the carbon source. Put them into a 250 mlconical flask and grow them at 28° C. with a 180 rpm rotate speedshaking. Measure the quantity of live bacteria in the fostering solutionat different time by means of a dilution flat method as to show thegrowth status of the bacteria. From the result shown below in table 5,one can conclude that all the three tested bacteria strains asPseudomonas sp.29, Bacillus sp. W31, and Bacillus cereus 45 can grow onthe Czapek agar medium which use experimental material as the carbonsource. After 10 days of growth, the quantity of bacteria was 600-2,500per ml, and after 20 days of growth, the quantity was up to40,000-60,000 per ml. TABLE 5 Alive bacteria quantity (per ml) Bacteria10 days 20 days Bacillus sp. W31   7 × 10² 6 × 10⁴ Bacillus cereus 45  6 × 10² 4 × 10⁴ Pseudomona sp. 29 2.5 × 10³ 6 × 10³

[0052] 4. Conclusion: The results of the colony diameter and thebacteria growth shown above prove that all the 7 kinds of microorganismscan utilize the experimental material as carbon and energy sources togrow. Therefore the experimental material is a biodegradable product.

EXAMPLE 6 Acute Toxicity Test of the Products of Vegetable FiberComposite Material of the Invention

[0053] Sample: disposable tableware produced by formula 1 of example 1

[0054] Institution in charge of detection: State Environment ProtectionAdministration of China, Beijing Institute of Environmental Medicine

[0055] Testing standard: refer to the requirements of toxicologicaldetection in “Universal technological conditions of railway fast foodlunchbox product supply” (TB/2611-94) in Professional Standard of theMinistry of Railways in the People's Republic of China, in which thesample is pretreated as follows: Weigh 30 g of sample and cut the sampleinto pieces of 0.5 cm×0.5 cm. Put the cut pieces into four sorbiticextractors, then respectively add 300 ml of distilled water, 300 ml of4% acetic acid, 300 ml of 65% alcohol, and 300 ml of n-hexane into eachextractor. Heat each extractor to the boiling points of above foursolvents and reflux them for 2 hr, in which the extractor containingwater and extractor containing 4% acetic acid were put into paraffinbathes, while the extractor containing 65% alcohol and extractorcontaining n-hexane were put into water bathes. Mix the four refluxliquids uniformly to form a mixture, and then place above mixture into arotary evaporator and depressurize and concentrate it at 70-75° C. toobtain a concentrated liquid. Take 100 ml of the concentrated liquid,add 2 g of starch into it, and then heat until it becomes a paste forexperimental use.

[0056] Testing method: experimental animal was Kunming breed miceweighing 13-22 g each, provided by the Animal Center of Chinese Academyof Medical Sciences.

[0057] (1) Trial test: 9 male and female mice randomly divided intothree groups separately, 3 mice in each group. Contamination dosages are20 g/kg, 19 g/kg, 5 g/kg respectively. Once contaminate through gastriclavage via mouth.

[0058] (2) Formal test: 40 male and female mice, randomly divided intofour groups respectively, 10 animals in each group. According to theresults of trial test, contamination dosages are 20 g/kg, 10 g/kg, 5g/kg, and 2.5 g/kg, once contaminated through gastric lavage via mouth.Fasting for 12 hr before gastric lavage, the maximum volume of dose was0.4 ml/20 g in body weight. Observe for one week after contamination,record the poisoning symptoms of animals and time of death. If LD₅₀ wasmore than 10 g/kg, it need not be calculated, while if LD₅₀ was lessthan 10 g/kg, determine it through retest using probability unit-graphmethod.

[0059] Experimental Results:

[0060] (1) Trial test: no death resulted in the three dosage groups ofmale and female animals, and no poisoning symptoms could be seen.

[0061] (2) Formal test: no death resulted in four dosage groups of maleand female animals, and no poisoning symptoms could be seen.

[0062] Measured LD₅₀ of delivered samples for detection being more than20 g/kg.

[0063] Results: lethal dose of 50% (LD₅₀) of above concentrated liquidis more than 20 g/kg, refer to acute toxicity (LD₅₀) grade scale, itbelongs to actual non-toxic grade.

[0064] This invention overcomes the defects of the published patentedtechnologies using shell or stalk of crops as main raw materials forproduction of disposable tableware, including complicated processes andhigh production costs. This invention provides a technology featuring asimple formula, lower cost of adhesives, attaining food sanitationstandards, single step forming with hot pressing as well as without theneed for long time drying and surface coating, yet still can achievesuch properties as water, heat and corrosion resistance, anti-freezing,non toxic, pollution free and biodegradable. This inventionscientifically and effectively utilizes agricultural waste, a rawmaterial of ample annual supply, and low costs. Further, disposablebiodegradable material and its products may be recovered, after theiruse, to make animal feed or fertilizer after being crushed into power,thus accomplishing the comprehensive utilization of recycled resources.The disposable biodegradable material and its products made with theprocess provided by this invention have the properties of being ofnatural color; dense, tough and tensile and constitute entirely newenvironment protection green products.

[0065] In summary, the above embodiments are only for describing theinvention but not for limiting the range of the invention. All thechanges that do not depart from the spirit of this invention are withinthe range of this invention.

What we claim is:
 1. A degradable composite material, which comprisesthe following components by weight in parts: plant fiber: 60-90 partsurea-formaldehyde resin 10-35 parts melamine resin  3-10 parts foodcoloring agent  1-10 parts

wherein the molecular weight of said urea-formaldehyde resin is 300-600.2. The degradable composite material according to claim 1, wherein theplant fiber is crop hull or stalk.
 3. The degradable composite materialaccording to claim 1, wherein the amount of the plant fiber is in therange of 70 to 80 parts by weight.
 4. The degradable composite materialaccording to claim 1, wherein the amount of urea-formaldehyde resin isin the range 10 to 20 parts by weight.
 5. The degradable compositematerial in according to claim 1, wherein the molecular weight of theurea-formaldehyde resin is 300-400.
 6. The degradable composite materialin according to claim 1, wherein the amount of the food coloring agentis in the range of 3 to 5 parts by weight.
 7. The degradable compositematerial according to claim 1, wherein the food coloring agent isselected from the group consisting of titanium white, zinc oxide, ironoxide red, pigment yellow 147, pigment blue 15, and combinationsthereof.
 8. The plant fiber composite material according to claim 7,wherein the food coloring agent is titanium white.
 9. A plant fibercomposite material according to claim 1, wherein the urea-formaldehydeis prepared by following steps: (1) adding 80-100 weight portions ofurea, 160-240 weight portions of formaldehyde (37%) and 16-24 weightportions of glycerol into a reaction vessel with an agitator and stirthem at a 60° C. until the urea is fully solved to form a first mixedsolution, cooling the first mixed solution to 20-25° C. and adding 5-10weight portions of sodium diphenylnaphthalenesulfonate and 2.5-7.5 partsby weight of Resorcin, then stirring above mixture for about 10-60minutes at a rotate speed of 120 rpm to form a second mixed solution;and (2) adjusting the pH value of the second mixed solution to 7-8 witha pH value conditioner, then stirring it for 30 minutes at a rotatespeed of 180-260 rpm, and stirring it for another 30 minutes at a rotatespeed of 300-400 rpm to form a third mixed solution, pouring the thirdmixed solution into a storage and drying it in the shade for 24 hours toobtain an urea formaldehyde resin base material, warming and drying theurea formaldehyde resin base material for 6 hours at 60° C., so as toobtain the final urea formaldehyde resin.
 10. The plant fiber compositematerial according to claim 9, wherein the pH value conditioner isselected from oxalic acid, acetic acid, phosphoric acid, andcombinations thereof.
 11. The plant fiber composite material accordingto claim 10, wherein the pH value conditioner is oxalic acid.
 12. Aplant fiber composite material according to claim 1, which comprises thefollowing components by weight in parts: crops shell or stalk powder of60 mesh 80 parts urea-formaldehyde resin 15 parts melamine resin  5parts food coloring agent  3 parts


13. A manufacturing method of the disposable tableware products usingthe degradable composite material according to claim 1, which comprisesthe following steps: (1) pulverizing a shell or stalk of plant cropsinto 60 mesh or over, and then thoroughly mixing the pulverized shell orstalk of crops with urea-formaldehyde resin and melamine resinproportionately to form a mixture of the degradable composite material;(2) feeding the mixture of the degradable composite material into aconcave molding mould positioned in an operating platform of apushing-upward-type oil hydraulic press in a fixed quantity and positionwith temperature of the mould maintained at 125-190° C.; and (3)controlling pressure of the pushing-upward-type oil hydraulic press atbetween 10-30 Mpa and keeping the press operates at 3 intervals bymaintaining at above pressure for 3-30 seconds per each interval, so asto obtain the finished products.
 14. The manufacturing method accordingto claim 13, wherein maintaining the concave mould temperature at 160°C., the convex mould temperature at 170° C., controlling workingpressure at 25 Mpa, keeping the press operates at 3 intervals bymaintaining at above pressure for 3-30 seconds per each interval.
 15. Amethod for using a degradable composite material according to claim 1for the production of tableware products, comprising: (1) feeding thedegradable composite material into a concave molding mould positioned inan operating platform of a pushing-upward-type oil hydraulic press in afixed quantity and position with temperature of the mould maintained at125-190° C.; and (3) controlling pressure of the pushing-upward-type oilhydraulic press at between 10-30 Mpa and keeping the press operates at 3intervals by maintaining at above pressure for 3-30 seconds per eachinterval, so as to obtain the finished products.
 16. Tableware productsmade from degradable composite material according to claim 1 and thatare nontoxic, degradable ecologically benign, and environmentallybeneficial, wherein the tableware products are made from a processcomprising: (1) feeding the degradable composite material into a concavemolding mould positioned in an operating platform of apushing-upward-type oil hydraulic press in a fixed quantity and positionwith temperature of the mould maintained at 125-190° C.; and (3)controlling pressure of the pushing-upward-type oil hydraulic press atbetween 10-30 Mpa and keeping the press operates at 3 intervals bymaintaining at above pressure for 3-30 seconds per each interval, so asto obtain the finished products.